Using pressure transients within a polymeric membrane for gas composition measurements

Abstract

The properties of polymeric membranes and measurements of gas concentrations are common elements of industrial processes and scientific research. Here we report a methodology whereby pressure measurements inside a closed polymeric membrane tube can be quantitatively related to the composition of the external gas. This approach is founded on the different rates at which the gases permeate into and out of the interior of the polymeric tube. The difference between the amounts of gas entering and leaving the tube triggers a pressure transient. The features of this transient depend on the species of the involved gases and their partial pressures and under certain conditions, allow the concentration of one or more species to be estimated. We outline the theoretical principles behind the proposed methodology and conduct laboratory tests on a device that could be adaptable to continuous measurements of CO2 partial pressure in field applications.